The present invention relates to apparatus for manipulating discrete commodities, especially to improvements in apparatus for manipulating groups of identical or similar commodities, such as groups of stacked sheets, plates, boards, foils or the like. More particularly, the invention relates to improvements in apparatus which serve to singularize groups of discontinuously supplied commodities (hereinafter referred to for convenience as stacks of paper sheets with the understanding, however, that the apparatus can treat other types of commodities with equal or similar facility), especially to singularize commodities which are supplied in groups forming files of closely or immediately adjacent commodities and being delivered to the singularizing location in a direction at right angles to the longitudinal direction of such files.
It is already known to singularize groups of neighboring stacks of paper sheets or the like by delivering such groups to a first conveyor which can be driven discontinuously at different speeds to advance successive groups into the range of a continuously driven accumulating or gathering conveyor. The latter is located ahead of a singularizing conveyor whose speed exceeds the speed of the gathering conveyor. Apparatus of such type are employed in or in conjunction with multi-track machines which turn out groups of neighboring stacks and whose output must be processed subsequent to completion of the singularizing step, e.g., for the purpose of inserting or otherwise introducing successive stacks into discrete cartons or other types of receptacles. The aforementioned multi-track machines may constitute or form part of production lines wherein large sheets of paper or the like are severed lengthwise and crosswise to yield smaller sheets which are accumulated into groups of stacks of superimposed smaller sheets. Each stack can constitute a ream or it may contain a different (larger or smaller) number of superimposed sheets. In such machines, several stacks of sheets (i.e., the aforementioned groups of e.g., five or seven neighboring stacks) are turned out at regular intervals, and successive groups must be converted into successive sections of a single row wherein the stacks are equally spaced apart from one another to allow for insertion of successive stacks into successive receptacles at regular intervals. A packing machine for stacks of superimposed sheets is disclosed, for example, in commonly owned U.S. Pat. No. 4,237,674 granted Dec. 9, 1980 to Kurt Aykut. The disclosure of this patent is incorporated herein by reference.
As a rule, successive groups of immediately or closely adjacent stacks are converted into a composite group wherein the stacks are immediately adjacent to each other, and such composite group is then converted into the aforementioned row of spaced-apart stacks which advance toward a packing or another consuming machine. For example, a tongs or another suitable gripper can be used to deliver successive groups of, for example, five neighboring stacks onto the aforementioned first conveyor of a conventional apparatus, and the first conveyor delivers successive groups onto the continuously driven gathering conveyor in order to convert successive groups into a single file of immediately adjacent (i.e., abutting) stacks. The tongs deliver successive groups at right angles to the longitudinal directions of such groups, and the first conveyor advances successive groups lengthwise, i.e., so that each group has a leader constituting one of the outermost stacks therein and a trailing portion constituting the other outermost stack. Such transport of successive groups from the first onto the gathering conveyor should result in elimination of gaps which necessarily develop between successive groups of stacks as a result of discontinuous or intermittent delivery of groups onto the first conveyor and intermittent operation of the first conveyor. In other words, the foremost stack of a next-following group must catch up with the rearmost stack of the preceding group not later than at the instant when the transfer of the next-following group from the first conveyor onto the gathering conveyor is completed. This is necessary because the formation of the aforementioned single row of spaced-apart equidistant stacks is facilitated (or is possible only) if the stacks of the group which is singularized as a result of transfer of its components from the gathering onto the singularizing conveyor are immediately adjacent to each other, i.e., if the neighboring stacks of the composite group (or at least of the front portion of the composite group) of stacks on the gathering conveyor are in actual abutment with one another.
The carrying out of the just discussed steps or operations in conventional gathering or accumulating and singularizing apparatus involves the utilization of complex, bulky and expensive controls and other instrumentalities, especially if such apparatus are used in or in conjunction with modern high-speed stack forming or producing machines which can turn out groups of several stacks each at a high frequency. A serious drawback of heretofore known gathering and singularizing apparatus is that they are likely to cause deformation or collapse of stacks and/or to damage certain sheets (especially the lowermost sheets) of the stacks, particularly when the apparatus of heretofore known design are used in or with high-speed stack forming and delivering machines. Shifting of sheets in certain stacks or in all of the stacks is particularly likely during abrupt acceleration or deceleration of stacks, e.g., during transfer of stacks from the first onto the gathering conveyor and/or from the gathering onto the singularizing conveyor of a conventional apparatus. Furthermore, heretofore known apparatus are incapable of transporting stacks or groups of stacks through greater distances such as would considerably exceed the length of a conveyor (i.e., which would necessitate pronounced and extended shifting of stacks relative to the conveyor means therebelow) because this would invariably entail smudging, crushing, creasing, curling and/or other damage to certain sheets, especially to the lowermost sheets of the stacks.